This invention relates generally to turbocharged gaseous fueled internal combustion engines. More particularly, but not by way of limitation, this invention relates to an improved exhaust gas recirculation system for a turbocharged gas engine for the purpose of reducing the emission of nitrogen oxides during combustion.
Many solutions have been offered to the problem of excessive nitrogen oxides in the exhaust gas of internal combustion engines. Among other solutions, it has been proposed that the recirculation of a portion of the exhaust gas into the combustion air will reduce nitrogen oxides and it has been proven that exhaust gas recirculation does in fact reduce nitrogen oxides. Many types of recirculation systems have been proposed for introducing a portion of the exhaust gas into the combustion air.
For example, U.S. Pat. No. 3,774,399 issued Nov. 27, 1973 to Hidetaka Nohira et al, describes a turbocharged internal combustion engine that is provided with an exhaust gas recirculation system. U.S. Pat. No. 3,672,340 issued June 27, 1972 to Georg A. Bomba describes an exhaust gas recirculation system for naturally aspirated internal combustion engines.
Many different types of recirculation systems have been proposed for exhaust gases and most are effective to some extent. Most of the systems require the use of some form of pump or blower to circulate the exhaust gas. Naturally, such auxiliary devices require the utilization of part of the engine horsepower and thus reduce the overall efficiency of the engine.
It is an object of this invention to provide an exhaust gas recirculation system for a turbocharged gaseous fuel engine that is very efficient and has low power requirements since the recirculation of the exhaust gas is accomplished by a differential pressure created within the system.